Attitude stability of a dual-spin satellite with a large flexible solar array

Abstract

Attitude stability criteria and nutation decay times for a dual-spin satellite with a large flexible solar array are found. Both rotor and platform damping are included. A continuum mechanics analysis of the solar array develops practical information regarding array natural modes, and these represent additional degrees of freedom. With proper mass balancing, the equations for spin variables can be decoupled from those for transverse variables. Assuming the solar array to be rigid, the ratio of rotor inertia to the geometric mean of the vehicle transverse inertias must be greater than unity for stability unless there is energy dissipation in the despun section. This is a significant extension of the major axis rule.' Upper and lower stability boundaries exist for the nutation damper damping constant and the damper performance is best at high nutation frequencies. Introducing array flexibility leads to modifications of the stability boundaries when the nutation frequency becomes close to an array natural frequency.